Friend of mine purchased an AI grenade when it came out and is now switching to a firecracker-based grenade that I created. 25 cents per grenade "toss and forget" vs 100$ "gotta run after my grenade" model.
He was disappointed with the efficiency of AI grenades (indoor use). Of course it is much more efficient then little firecracker grenades with BBs but when you can make 40 such grenades for 10$, the choice is easy
I have never been impressed by the AI grenade in action myself.